Question

A plane leaves an airport and flies south at 120 mph. Later, a second plane leaves the same airport and flies south at 300 mph. If the second plane overtakes the first one in
5
1
2
hours, how much of a head start did the first plane have?

Answer 1

Are there 3 questions here ??

I will consider the last one, so it would read:
"A plane leaves an airport and flies south at 120 mph. Later, a second plane leaves the same airport and flies south at 300 mph. If the second plane overtakes the first one in 2 hours, how much of a head start did the first plane have?"

in effect the second plane is gaining on the first plane at 180 mph, so in 2 hours it would have to make up 360 miles, which would be the head-start.

check: distance covered by slower plane = 360 + 120(2) = 600
distance covered by faster plane = 300(2) = 600
My answer is correct.

do the other two problems in the same way

Answer 2

300*5 = 120*5 + 120x

Solve for x. Do the same for 1 and 2.